Development of Operational Unstructured Model Storm Surge Guidance: Demonstration of Skill for Katrina

Since 2012 the U.S. National Oceanic and Atmospheric Administration/National Ocean Service/Office of Coast Survey (NOAA/NOS/OCS) has used the ADvanced CIRCulation (ADCIRC) hydrodynamic model to provide operational guidance for extratropical storm water levels (i.e., storm surges and tides). ADCIRC is an unstructured finite element model with grids that efficiently localize resolution within a large domain, it solves the fully non-linear shallow water equations, and it has conducted experimental coupled surge-tide-wave-river total water simulations. OCS is now testing and transitioning a tropical storm surge and tide model for the East and Gulf coasts with coastal resolution that reaches 200 m. This model predicts water levels and overland coastal flooding based upon an ensemble of perturbations from the official National Hurricane Center Advisories. This model has been validated against more than ten significant tropical storm surge events and is being transitioned to operational use as part of a multi-model ensemble strategy for predicting storm surges, along with the Sea, Lakes, and Overland Surges from Hurricanes (SLOSH) model.

Using Hurricane Katrina, the skill of this future operational model is demonstrated via a hindcast of the event. The operational configuration of the model is also used in pseudo-forecast mode to demonstrate how ensemble guidance could be provided for a Katrina event. Since this model is part of a multi-model ensemble, analysis of this guidance is made alongside the guidance from the operational National Weather Service storm surge model SLOSH to demonstrate the importance of an ensemble approach for predicting coastal inundation.